Re: [PATCHv2] sctp: Don't add the shutdown timer if its already been added

["Jere Leppänen" <jere.leppanen@nokia.com>]

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On Thu, 30 Apr 2020, Marcelo Ricardo Leitner wrote:

> On Wed, Apr 29, 2020 at 07:36:13AM -0400, Neil Horman wrote:
> > This BUG halt was reported a while back, but the patch somehow got
> > missed:
> > 
> > PID: 2879   TASK: c16adaa0  CPU: 1   COMMAND: "sctpn"
> >  #0 [f418dd28] crash_kexec at c04a7d8c
> >  #1 [f418dd7c] oops_end at c0863e02
> >  #2 [f418dd90] do_invalid_op at c040aaca
> >  #3 [f418de28] error_code (via invalid_op) at c08631a5
> >     EAX: f34baac0  EBX: 00000090  ECX: f418deb0  EDX: f5542950  EBP: 00000000
> >     DS:  007b      ESI: f34ba800  ES:  007b      EDI: f418dea0  GS:  00e0
> >     CS:  0060      EIP: c046fa5e  ERR: ffffffff  EFLAGS: 00010286
> >  #4 [f418de5c] add_timer at c046fa5e
> >  #5 [f418de68] sctp_do_sm at f8db8c77 [sctp]
> >  #6 [f418df30] sctp_primitive_SHUTDOWN at f8dcc1b5 [sctp]
> >  #7 [f418df48] inet_shutdown at c080baf9
> >  #8 [f418df5c] sys_shutdown at c079eedf
> >  #9 [f418df70] sys_socketcall at c079fe88
> >     EAX: ffffffda  EBX: 0000000d  ECX: bfceea90  EDX: 0937af98
> >     DS:  007b      ESI: 0000000c  ES:  007b      EDI: b7150ae4
> >     SS:  007b      ESP: bfceea7c  EBP: bfceeaa8  GS:  0033
> >     CS:  0073      EIP: b775c424  ERR: 00000066  EFLAGS: 00000282
> > 
> > It appears that the side effect that starts the shutdown timer was processed
> > multiple times, which can happen as multiple paths can trigger it.  This of
> > course leads to the BUG halt in add_timer getting called.
> > 
> > Fix seems pretty straightforward, just check before the timer is added if its
> > already been started.  If it has mod the timer instead to min(current
> > expiration, new expiration)
> > 
> > Its been tested but not confirmed to fix the problem, as the issue has only
> > occured in production environments where test kernels are enjoined from being
> > installed.  It appears to be a sane fix to me though.  Also, recentely,
> > Jere found a reproducer posted on list to confirm that this resolves the
> > issues
> > 
> > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> > CC: Vlad Yasevich <vyasevich@gmail.com>
> > CC: "David S. Miller" <davem@davemloft.net>
> > CC: Jere Leppänen <jere.leppanen@nokia.com>
> > CC: marcelo.leitner@gmail.com
> > 
> > ---
> > Change notes:
> > V2) Updated to use timer_reduce
> 
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Hey is this patch falling through the cracks again? No rush, I'm just 
wondering what's going on.